Add multilingual multihost support

This commit adds multihost support when more than one language is configured and `baseURL` is set per language.

Updates #4027

hugolib/page.go

@@ -1754,6 +1754,11 @@ func (p *Page) shouldAddLanguagePrefix() bool {
 		return false
 	}
 
+	if p.s.owner.IsMultihost() {
+		// TODO(bep) multihost check vs lang below
+		return true
+	}
+
 	if p.Lang() == "" {
 		return false
 	}